The present invention relates to positive displacement engines and, more particularly, to a novel engine in which the combustion chamber is separated from piston chambers which receive hot gases from the combustion chamber.
The engine of the invention is thermodynamically similar to the Brayton or Joule cycle, while physically resembling the Otto cycle engine in that it utilizes one or more pistons or other positive displacement devices for compression and power. Combustion is external of the positive displacement chambers, thereby providing many advantages. The use of a combustion chamber separated from the positive displacement chambers provides greater flexibility in the form of fuel employed. Thus, solid, liquid or gaseous fuel may be utilized. The combustion temperature may be lower and the combustion time longer, resulting in more complete combustion, to thereby substantially reduce the level of pollutants in the exhaust. In addition, no critical ignition timing is necessary in such an arrangement. One or more pistons, or a portion of the operating cycle of the pistons, is utilized to compress air which is passed through a heat exchanger to be preheated while cooling exhaust gases and which is then introduced into the combustion chamber. Excess compressed air may be stored in an accumulator for subsequent use when necessary, for example, during periods of peak power demand or when the engine is cold.
During braking, regenerative braking may be achieved whereby the engine is slowed while compressing air in the compressor which is passed to an accumulator for storage and subsequent use when needed. The compressor may be disconnected on start-up so that there is very low starting torque. The stored compressed air is also available for powering auxiliary equipment as well as meeting peak power demands and upon engine start-up. The availability of compressed air for start-up provides easy cold weather starting and if desired enables the fuel to be cut off completely on idle since the engine can be restarted immediately on demand in view of the availability of compressed air which can be passed through the system to the positive displacement chambers.
The engines of the invention may in appropriate sizes be employed in a wide variety of applications. For example, when employed to power an automobile, the engine of the invention would have increased efficiency, reduced exhaust levels, fast starting capability, compressed air availability, dynamic braking, and instant power availability. For buses and trucks, the savings of braking energy would be a particularly significant factor. The engines would also find application in locomotives, stationary power plants, farm tractors, marine engines, airplanes, etc. A primary advantage of use in an airplane would be high horsepower availability for the size of the engine during take-off because of the availability of the compressed air for maximum torque as a take-off assistant.
The above and other objects, features and advantages of the invention will become more apparent as this description proceeds.